玉川上水の植生状態と鳥類群集

<p>The vegetation of the Tamagawa-josui Canal, which is a precious urban green belt running through an area of Tokyo, varies according to tree management practices. We recorded the species and individual numbers of birds (seven times) and measured tree diameters (18 plots) at four sites along the canal in 2021. At Mitaka and Kodaira, where woods along the canal were rich and green patches were also available near the canal, the bird communities were rich. In contrast, at Suginami, where the canal was sandwiched between heavily used roads and green patches were limited, species numbers and populations of birds were comparatively poor. The Azure-winged Magpie (Cyanopica cyanus), the Jungle Crow (Corvus macrorhynchos) and the Rock Dove (Columba livia) were relatively abundant. The bird community was poorest at Koganei, where only cherry trees were planted and other trees were cleared, although a big park was available near the canal. Forest dwelling birds were particularly few and only birds adaptable to urbanized environments, such as the White-cheeked Starling (Sturnus cineraceus) and the Tree Sparrow (Passer montanus) were relatively abundant. The pattern of seasonal changes in bird populations at Tamagawa-josui Canal closely resembled those seen at the Imperial Palace and Akasaka Imperial Residence in central Tokyo. The Brown-eared Bulbul (Hypsipetes amaurotis) and other forest dwelling birds decreased in summer. The results of the present study suggest that the bird communities along the Tamagawa-josui Canal are affected by the ambient vegetation, which is a direct result of anthropogenic management practices. We note the necessity to evaluate this perspective on biodiversity for the future vegetation management of this canal.</p>